I don't believe stem tea is really going to work very well for you. Yeah, you'll hear a shitload of stories about how THC tea "mellows you out" or how it gives you a buzz that lasts the whole day. Well, in my opinion that's all **.
First, THC isn't water soluble at all. And there's not very much THC in the stems to begin with. In fact, even if you used a whole plant's worth of stems and leaves to make one pot of tea, nothing would really happen for you. The chemical reactions needed to get you high just won't occur that way.
However, if you wan't to combine them with butter and then bake with it, you might as well throw those stems into to the butter mix. Just make sure they're ground and pulverized to a fine powder with something like a coffee grinder. You don't wanna be chewing on them in your brownies or whatever. Also get the seeds out of there, of course.
Dunno, the weed tea might taste good though.
Now, if you are bound and determined to get your weed in a hot drink form, you can always mix warm alcoholic drinks that call for hot butter and substitute it with bud butter. A hot butter scotch toddy, for example. Heh, now that packs one helluva wallop, my friend.